I just bought a 91 firebird base. The stock motor according to VIN is 305 TBI. When I checked car over and purchased noticed it was carb'd and didnt look like a 305. Can someone please help me locate possible engine codes or something. I know its chevy motor. It has mechanical fuel pump and spark plugs stick straight out of block, no angle to plugs at all. I will try and post pics later if needed. Thanks ahead of time.

 

Find the RPO code list on the car. It will either be in the center console or in the keyed rear hatch compartment.

It's a sticker with a bunch of 3 digit codes on it.
Look for one of the following codes.

LB9--5.0 TPI
LHO--3.1 V6
LO3--5.0 TBI
L98--5.7 TPI

As far as identifying the engine that you have...... There is a spot on the front passenger side of the block that should have some numbers stamped in it. Those numbers should match the last 8 characters of your vin. Good luck

 

He alread knows what the "codes" say his engine came from the factory as. Looking that up some more is pretty much a waste of time. Seeing if the VIN portion of the stamping might be helpful though; that will at least tell him if the engine has been changed.

For that matter, "looking up" any "codes" at all is pretty much a waste of time. Because small block Chevy parts are SO interchangeable, it is vanishingly rare to EVER find such an engine that was simply swapped into another car, lock stock & barrel, with all of its original parts, such that its "codes" would contain any useful info at all.

It's actually entirely possible though, and fairly likely at that, that the engine is really just the original one for the car, but somebody put a carb on it. Happens all the time.

You can't tell what displacement a small block Chevy is by things like

They all look the same.

The bore of the block will be revealed by its casting number. That is on the top of the bell housing flange, right behind and below the driver's side head, sort of below the windshield wiper motor. That number DOES NOT LIE. It will tell you if it's a 305, 302/327/350 (they can all be built from the same blocks), 400, and so on.

The head casting number will tell you if the heads are the same as the car's originals. There is an ENORMOUS variety of SBC heads out there. Most are terrible, including the TBI 305 ones; a few are OK; and even fewer are REALLY GOOD. That number is under the valve covers, between the rocker arms.

Get the block and head casting #s and we can tell you a great deal about what it is, but only to a point.

Other things that determine what the engine's identity is are a little harder to find by inspection. The pistons could be flat-tops, or they could be dished. Hard to see without tearing it down. Same for the cam: very difficult to identify except by precise measurements of lifter motion vs rotation. Very very tedious. And of course, those are VERY often replaced either during a rebuild, or by owners looking for some sort of change in the engine's performance.

About everything else is just a bolt-on, and isn't part of the "engine" proper.

For the most part, there's not alot of sense in worrying about what you've got, unless you're trying to buy internal parts for it. Other than that, maintain the best you can, keep it running as perfect as possible, and find out stuff as you go. There are all sorts of oddball clues that can pop up from time to time, that are far too numerous to mention.

 

Thanks for the input. I really appreciate the help. Ill look for the block numbers tomorrow in daylight. The reason of knowing what I have is to buy parts for it. I would like to buy some headers and it badly
Needs a tune up. Im just trying to make it easy as possible to buy parts. i hate guessing games. Also I have an antifreeze look that is coming from drivers side undercar back side of motor. I'm thinking its a
Freeze plug but not sure. It doesn't leak while its running or driving. I did puddle from car sitting overnight. If its freeze plug can I change it with motor in car or no. The car also has factory motor harness in it just laying accross the motor does anyone have a diagram of what wires I need and dont need I really just wanna clean up the engine bay. It looks cluttered. Thanks again for all the help.

 

SBC headers all fit the same; doesn't matter what motor it is. Get whatever ones are of suitable quality, fit, tubing sizes, etc. to fit your goals.

None of the numbers is of any help about tune-up parts, except if your heads are from the very early 70s or older. None of the numbers on the engine will tell you that except the head casting #s. Most likely though, pull out a plug, see what it is, and get one that physically matches; which would most likely be, AC/Delco R44T if they're washer seat (old old old old), or R45TS if they're tapered seat (about 71 or newer).

As far as the wiring, tie-wraps and split-tubing loom are your friend. Don't cut anything. Without knowing how much professionalism and finesse were applied or what kind of hack job was done putting this motor in, it's impossible to guess over the Internet which ones the installer put where; and without knowing what changes they made (V8 in a 6-cyl car, a carb in a TBI car, etc.) if any, impossible to guess which ones are doing anything, which ones aren't and can be coiled back, and which ones should be but aren't.

You gotta understand, the SBC motor has been around since 1955. It has come in CIDs od 262.5, 265, 267, 283, 302, 305, 307, 327, 350, and 400; and there are also other popular combinations that can be built with either a little imagination of aftermarket parts, notably the 383 (which has the 302/327/350 4" bore in whatever oversize, with the 400 3.75" stroke). EVERY SBC head will bolt to EVERY SBC block from 1955 to 2000 with the exception of the LT1. An engine that has been swapped ALMOST ALWAYS is composed of random parts from various years since they all bolt up and some are FAR more common than others. There is a dizzying array of aftermarket parts of all sorts that can be bought. In short, the odds that your engine is a purely factory creation of any sort, are basically zero, unless it's the original one for your car.

Avoid the whole "clean up the engine bay" idea. It is BAD. That's nothing but hilljack-ish for "hack off whatever I don't know what it does", dressed up in language that makes it sound like something positive, which it isn't. Make an effort BEFORE doing ANY of that, to LEARN what all that stuff is and does. There is no benefit to your castings being visible; the engine will run just as well, and most likely better, with all the stuff it came with, intact and operating. All those hoses and wires were put there for a purpose: the factory doesn't just randomly add stuff for no reason. Before turning your car into an even more thorough hack job than however it might happen to be now, learn and understand what that stuff does.

 

Ok thanks for the input. I found the casting number thanks to b4ccamaro. It is the original 305. They just changed intake and added carb. I dont know about the heads. But good idea with the spark plugs. The engine bay as far as wires and cleaning up. I know its factory harness but the ends of the harness do not plug into anything at all they are just laying on top of the valve covers so Im guessing they were for the fuel injection or intake stuff. Is there a post on removing the smog canister, smog pump, etc. I am just trying to make the car simple. I used to have a 91 camaro that was all original 305 TBI and it ran great and all that but I felt like I couldnt tinker with it without screwing somthing up so I always had that nag to make it Carb'd. But anyways that cars gone now. But since this firebird came into play and found it was carb'd I jumped on that deal. I like tinkering and I like simple so any help is surely appreciated. Sorry for talking so much. I have no one to talk to here about cars and stuff, its just my wife, me, and my two Rottweilers and they dont talk back. LOL. Thanks again. Talk to you all later.